There are over 50 distinct collections in the Lear Center. Premier manuscript collections include the Lear-Carson Collection, a research archive of the life and work of Rachel Carson, the Sheaffer-O'Neill Collection of manuscripts, photographs, documents, and important editions of Eugene O'Neill, the Prudence Crandall Collection, containing letters and personal papers of the nineteenth-century Connecticut education and civil rights pioneer, and the Lear-Potter Collection, a research archive of the life and work of Beatrix Potter. Important book collections include the Helen O. Gildersleeve Collection of Children's Books and the Timothy Green Collection of 18th century New London imprints. Among the major art collections are the Chu-Griffis Asian Art Collection, with over 250 Chinese paintings, calligraphic scrolls, and Japanese woodcuts and the Artists' Books Collection with nearly 200 artists' books in a variety of formats.

Collections may be browsed by one of three methods: by format, by subject, or by author. Many collections may be listed in more than one index.